Hydrogen production from biological systems under different illumination conditions

Hydrogen is a natural by-product of several microbial driven biochemical reactions, mainly in anaerobic fermentation processes. In addition, certain microorganisms produce enzymes by which H₂ from water may be obtained if an outside energy source, like sunlight, is provided. Biophotolysis is a biological process which involves solar energy and algae clusters to convert water into hydrogen. Algae pigments absorb solar energy and enzymes in the cell act as catalysts to split water into hydrogen and oxygen. There are many research activities studying hydrogen production from biological systems cyanobacteria and green algae and some studies present a complete outline of the main available pathways to improve the photosynthetic H₂ production [1] and [2].Efficiency (energy produced from hydrogen divided by solar energy) of such processes can be estimated up to 10%. This value has to be increased for a large-scale hydrogen production. The effect of different artificial illumination conditions on H₂ production was studied for green algae cultures (Chlamydomonas reinhardtii). Results will be used to design a high-efficiency photobioreactor for a large-scale hydrogen production.     

Biological hydrogen production by Anabaena sp. - Yield, energy and CO2 analysis including fermentative biomass recovery

This paper presents laboratory results of biological production of hydrogen by photoautrotophic cyanobacterium Anabaena sp. Additional hydrogen production from residual Cyanobacteria fermentation was achieved by Enterobacter aerogenes bacteria. The authors evaluated the yield of H₂ production, the energy consumption and CO₂ emissions and the technological bottlenecks and possible improvements of the whole energy and CO₂ emission chain.The authors did not attempt to extrapolate the results to an industrial scale, but to highlight the processes that need further optimization.The experiments showed that the production of hydrogen from cyanobacteria Anabaena sp. is technically viable. The hydrogen yield for this case was 0.0114 kgH₂/kg_biomass which had a rough energy consumption of 1538 MJ/MJH₂ and produced 114640 gCO₂/MJH₂. The use of phototrophic residual cyanobacteria as a substrate in a dark-fermentation process increased the hydrogen yield by 8.1% but consumed 12.0% more of energy and produced 12.1% more of CO₂ showing that although the process increased the overall efficiency of hydrogen production it was not a viable energy and CO₂ emission solution. To make cyanobacteria-based biofuel production energy and environmentally relevant, efforts should be made to improve the hydrogen yield to values which are more competitive with glucose yields (0.1 kgH₂/kg_biomass). This could be achieved through the use of electricity with at least 80% of renewables and eliminating the unessential processes (e.g. pre-concentration centrifugation).     

Fabrication of WO3 based nanocomposites for the excellent photocatalytic energy production under visible light irradiation

Energy crisis and higher demands have lead scientists to search for economic and reliable sources of energy. In this research work, WO₃/BiVO₄ (1%,2%,3% and 4%) composites are synthesized by using a facile hydrothermal method to produce hydrogen energy from biomass through photoelectrochemical cells. The photoanodes were made by using spin coating methods. The experimental results were analyzed by the SEM, XRD, UV–Vis, PL, and BET spectroscopic techniques. The XRD results showed that the material is crystalline and the average crystallite size is in the range of 50–55 nm, the SEM results showed that the materials have spheres-like nanostructures. The UV and PL results exhibited that absorption region increased and recombination rate decreased by adding BiVO₄ up to 3%. The BET results showed the porosity of the material and exhibited that WO₃/BiVO₄ (3%) has a large surface area (m²/g). The efficiency was analyzed by producing hydrogen energy and the results revealed that WO₃/BiVO4 (3%) showed the highest efficiency for producing hydrogen energy, which is 330.9 micro-mol.h⁻¹.g⁻¹. The material also showed excellent stability even after the third cycle. The extraneous efficiency caused due to redshift of the WO₃/BiVO₄(3%), high redox potential, high crystallinity, small bandgap and electronic interaction across the electrodes for the production of hydrogen gas fuel during efficient photocatalytic activity. Moreover, WO₃/BiVO₄ (3%) is proved to be an active and favourable photocatalyst for the production of hydrogen energy from biomass/bio-wastes, which can be further utilized in various energy applications.     

Comparison between heterofermentation and autofermentation in hydrogen production from Arthrospira (Spirulina) platensis wet biomass

Hydrogen production from Arthrospira (Spirulina) platensis wet biomass through heterofermentation by the [FeFe] hydrogenase of hydrogenogens (hydrogen-producing bacteria) and autofermentation by the [NiFe] hydrogenase of Arthrospira platensis was discussed under dark anaerobic conditions. In heterofermentation, wet cyanobacterial biomass without pretreatment was hardly utilized by hydrogenogens for hydrogen production. But the carbohydrates in cyanobacterial cells released after cell wall disruption were effectively utilized by hydrogenogens for hydrogen production. Wet cyanobacterial biomass was pretreated with boiling and bead milling, ultrasonication, and ultrasonication and enzymatic hydrolysis. Wet cyanobacterial biomass pretreated with ultrasonication and enzymatic hydrolysis achieved the maximum reducing sugar yield of 0.407 g/g-DW (83.0% of the theoretical reducing sugar yield). Different concentrations (10 g/l to 40 g/l) of pretreated wet cyanobacterial biomass were used as substrate to produce fermentative hydrogen by hydrogenogens, which were domesticated with the pretreated wet cyanobacterial biomass as carbon source. The maximum hydrogen yield of 92.0 ml H₂/g-DW was obtained at 20 g/l of wet cyanobacterial biomass. The main soluble metabolite products (SMPs) in the residual solutions from heterofermentation were acetate and butyrate. In autofermentation, hydrogen yield decreased from 51.4 ml H₂/g-DW to 11.0 ml H₂/g-DW with increasing substrate concentration from 1 g/l to 20 g/l. The main SMPs in the residual solutions from autofermentation were acetate and ethanol. The hydrogen production peak rate and hydrogen yield at 20 g/l of wet cyanobacterial biomass in heterofermentation showed 110- and 8.4-fold increases, respectively, relative to those in autofementation.     

Performance of nano photocatalysts for the recovery of hydrogen and sulphur from sulphide containing wastewater

Stability of photocatalyst plays an important role in efficient hydrogen recovery from sulphide waste streams. This research focuses on the stability and efficiency of visible light active photocatalysts viz., RuO₂/CuGa_1.6Fe_0.4O₄, ZnFe₂O₃, (CdS + ZnS)/Fe₂O₃ and Ce/TiO₂ for H₂ production. RuO₂/CuGa_1.6Fe_0.4O₄ photocatalyst was found to give maximum hydrogen production of 8370 μmol/h. The reusability of the photocatalysts was tested by multiple cycles of catalyst regeneration along with H₂ production. The result shows that (CdS + ZnS) coated iron oxide core shell particles were found to be stable than other prepared nano photocatalysts. It is also demonstrated that H₂S can be split into hydrogen and sulphur under visible light irradiation using sulphide and sulphite reaction media at room temperature. This research paper will help in search of stable photocatalysts in recovering hydrogen from sulphide wastewater along with sulphur separation.     

Preformance analysis of a water splitting reactor with hybrid photochemical conversion of solar energy

In this paper, a new hybrid system for hydrogen production via solar energy is developed and analyzed. In order to decompose water into hydrogen and oxygen without the net consumption of additional reactants, a steady stream of reacting materials must be maintained in consecutive reaction processes, to avoid reactant replenishment or additional energy input to facilitate the reaction. The system comprises two reactors, which are connected through a proton conducting membrane. Oxidative and reductive quenching pathways are developed for the water reduction and oxidation reactions. Supramolecular complexes [{(bpy)₂Ru(dpp)}₂RhBr₂] (PF₆)₅ are employed as the photo-catalysts, and an external electric power supply is used to enhance the photochemical reaction. A light driven proton pump is used to increase the photochemical efficiency of both O₂ and H₂ production reactions. The energy and exergy efficiencies at a system level are analyzed and discussed. The maximum energy conversion of the system can be improved up to 14% by incorporating design modification that yield a corresponding 25% improvement in the exergy efficiency.     

Transition to hydrogen economy in the United States: A 2006 status report

Energy crises in the latter part of the 20th century, as well as the current increase in the cost of oil, emphasize the need for alternate sources of energy in the United States. Concerns about climate change dictate that the source be clean and not contribute to global warming. Hydrogen has been identified as such a source for many years and the transition to a hydrogen economy was predicted to occur from the mid-1970s to 2000. This paper reports on the status of this transition in the year 2006. Instead of being a clean source of energy, most of the hydrogen produced in the US results from steam reforming of fossil fuels, releasing _CO2${\mathrm{CO}}_2$ and other pollutants to the atmosphere. Nuclear process heat is ideally suited for the production of hydrogen, either using electricity for electrolysis of water, or heat for thermochemical hydrogen production or reforming of fossil fuels. However, no new nuclear plants have been ordered or built in the United States since 1979, and it may be many years before high-temperature nuclear reactors are available for production of hydrogen. Considerable research and development efforts are focused on commercializing hydrogen-powered vehicles to lessen the dependence of the transportation sector on imported oil. However, the use of hydrogen fuel cell vehicles (FCV) in 2006 is two orders-of-magnitude less than what has been predicted. Although it makes little sense environmentally or economically, hydrogen is also used as fuel in internal combustion engines. Development of hydrogen economy will require a strong intervention by external forces.     

Efficiency of hydrogen production systems using alternative nuclear energy technologies

Nuclear energy can be used as the primary energy source in centralized hydrogen production through high-temperature thermochemical processes, water electrolysis, or high-temperature steam electrolysis. Energy efficiency is important in providing hydrogen economically and in a climate friendly manner. High operating temperatures are needed for more efficient thermochemical and electrochemical hydrogen production using nuclear energy. Therefore, high-temperature reactors, such as the gas-cooled, molten-salt-cooled and liquid-metal-cooled reactor technologies, are the candidates for use in hydrogen production. Several candidate technologies that span the range from well developed to conceptual are compared in our analysis. Among these alternatives, high-temperature steam electrolysis (HTSE) coupled to an advanced gas reactor cooled by supercritical CO₂ (S-CO₂) and equipped with a supercritical CO₂ power conversion cycle has the potential to provide higher energy efficiency at a lower temperature range than the other alternatives.     

Costless and huge hydrogen yield by manipulation of iron concentrations in the new bacterial strain Brevibacillus invocatus SAR grown on algal biomass

There is a growing global demand on bio-hydrogen production (BHP) using costless and wastes material. Herein we demonstrate the possibility to produce high yield of hydrogen using a new bacterial strain grown on acidic hydrolyzed cyanobacterial biomass as a costless carbon feedstock under various iron concentrations. We used E. coli DH701 mutant and new strain Brevibacillus invocatus SAR isolated from Assiut city soil samples. The mentioned new strain was identified morphologically, biochemically and by molecular analysis using 16S rDNA sequence. Limitation of iron induced BHP in tested cyanobacteria. Iron concentration (0.045 mM) enhanced hydrogenase activity and cumulative hydrogen evolution in the investigated cultures. B. invocatus yielded 3.3 mol H₂/mole glucose and 3.8 mol H₂/mole reducing sugar (algal biomass), while the mutant strain yielded 1.78 mol H₂/mole glucose and 3.4 mol H₂/mole reducing sugar (algal biomass). Thus, the use of algal biomass induced higher potency of BHP especially at 0.045 mM iron.     

Hydrogen production from phototrophic microorganisms: Reality and perspectives

Hydrogen is a promising alternative to fossil fuel for a source of clean energy due to its high energy content. Some strains of phototrophic microorganisms are known as important object of scientific research and they are being explored to raise biohydrogen (BioH₂) yield. BioH₂ is still not commonly used in industrial area because of the low biomass yield and valuable down streaming process. This article deals with the methods of the hydrogen production with the help of two large groups of phototrophic microorganisms – microalgae and cyanobacteria. Microalgal hydrogen is environmentally friendly alternative to conventional fossil fuels. Algal biomass has been considered as an attractive raw source for hydrogen production. Genetic modified strains of cyanobacteria are used as a perspective object for obtaining hydrogen. The modern photobioreactors and outdoor air systems have been used to obtain the biomass used for hydrogen production. At present time a variety of immobilization matrices and methods are being examined for their suitability to make immobilized H₂ producers.     

Hydrogen production from methane and solar energy – Process evaluations and comparison studies

Three conventional and novel hydrogen and liquid fuel production schemes, i.e. steam methane reforming (SMR), solar SMR, and hybrid solar-redox processes are investigated in the current study. H₂ (and liquid fuel) productivity, energy conversion efficiency, and associated CO₂ emissions are evaluated based on a consistent set of process conditions and assumptions. The conventional SMR is estimated to be 68.7% efficient (HHV) with 90% CO₂ capture. Integration of solar energy with methane in solar SMR and hybrid solar-redox processes is estimated to result in up to 85% reduction in life-cycle CO₂ emission for hydrogen production as well as 99–122% methane to fuel conversion efficiency. Compared to the reforming-based schemes, the hybrid solar-redox process offers flexibility and 6.5–8% higher equivalent efficiency for liquid fuel and hydrogen co-production. While a number of operational parameters such as solar absorption efficiency, steam to methane ratio, operating pressure, and steam conversion can affect the process performances, solar energy integrated methane conversion processes have the potential to be efficient and environmentally friendly for hydrogen (and liquid fuel) production.     

Automatic high-pressure H2 generation up to 40 MPa through HCO3−/CO32− enhanced Al–H2O reaction

For the practical application, storage, and transportation of hydrogen energy, compressed high-pressure H₂ is generally required, which consumes large amounts of energy. In this research, an automatic high-pressure H₂ production system based on the HCO₃^? enhanced Al–H₂O reaction is established, in which, over 40 MPa H₂ at 300 °C (25 MPa at 25 °C) is successfully obtained without using any compressing facilities. Energy balance calculation reveals that although this reaction requires a high temperature, it is highly exothermic (145.9 MJ/kg H₂). Since heating the reactants to the desired reaction temperature only needs an energy of 55.3 MJ/kg H₂, the energy requirement of this reaction can be self-supported. In addition, waste Al-can is further tested for the high-pressure H₂ generation to realize a waste material recovery simultaneously, and over 40 MPa H₂ at 300 °C can also be obtained with the addition of Na₂CO₃. This research proposes a new way of automatic high-pressure H₂ production from renewable resources, which can promote the practical large-scale hydrogen energy utilization.     

Production of hydrogen for export from wind and solar energy,natural gas,and coal in Australia

Hydrogen production for export to Japan and Korea is increasingly popular in Australia. The theoretically possible paths include the use of the excess wind and solar energy supply to the grid to produce hydrogen from natural gas or coal. As a contribution to this debate, here I discuss the present contribution of wind and solar to the electricity grid, how this contribution might be expanded to make a grid wind and solar only, what is the energy storage needed to permit this supply, and what is the ratio of domestic total primary energy supply to electricity use. These factors are required to determine the likeliness of producing hydrogen for export. The wind and solar energy capacity, presently at 6.7 and 11.4 GW, have to increase almost 8 times up to values of 53 and 90 GW respectively to support a wind and solar energy only electricity grid for the southeast states only. Additionally, it is necessary to build-up energy storage of actual power >50 GW and stored energy >3000 GW h to stabilize the grid. If the other states and territories are considered, and also the total primary energy supply (TPES) rather than just electricity, the wind and solar capacity must be increased of a further 6–8 times. It is concluded that it is extremely unlikely that hydrogen for export could be produced from the splitting of the water molecule by using excess wind and solar energy, and it is very unlikely that wind and solar may fully cover the local TPES needs. The most likely scenario is production hydrogen via syngas from either natural gas or coal. Production from natural gas and coal needs further development of techniques, to include CO₂ capture, a way to reuse or store CO₂, and finally, the better energy efficiency of the conversion processes. There are several challenges for using natural gas or coal to produce hydrogen with near-zero greenhouse gas emissions. Carbon capture, utilization, and storage technologies that ensure no CO₂ is released in the production process, and new technologies to separate the oxygen from the air, and in case of natural gas, the water, and the CO₂ from the combustion products, are urgently needed to make sense of the fossil fuel hydrogen production. There is no benefit from producing hydrogen from fossil fuels without addressing the CO₂ issue, as well as the fuel energy penalty issue during conversion, that is simply translating in a net loss of fuel energy with the same CO₂ emission.     

Effects of nanofluids on the photovoltaic thermal system for hydrogen production via electrolysis process

In this study the photovoltaic hybrid thermal system has been fabricated for an effective increase in production of electric output. Further the PV/T system also designed to produce the hydrogen from the water through electrolysis process. Several studies reported drastic reduction in the electric output due to high cell temperatures. Nevertheless, these effects are reduced by introduction of the nanoparticles. This study also examines the nanofluids MWCNT and Fe₂O₃ as the passive cooling agent for higher electric output production without any major energy loss. The nanoparticles are dispersed in the water at the optimum fashions to increase the thermal and electrical efficiency of the system. Both MWCNT and Fe₂O₃ nanofluids were passed to the hybrid system at the flow rate of 0.0075 kg/s and 0.01 kg/s. The highest electrical output and thermal efficiency has been obtained at 12.30 P.M. With regard to the production of hydrogen, the maximum productions were observed from 12.15 P.M. to 13.00 P.M.. Implementation of this method compensates the energy loss with superior electrical output compared to previous conventional method. By compelling the results, 0.01 kg/s subjected to be efficient on the electricity production and the hydrogen generation. Further, employing the electrolyzer as the attached to the hybrid system produces the hydrogen, which can be stored for future use as the promising source of energy.     

Water-splitting mechanism analysis of Sr/Ca doped LaFeO3 towards commercial efficiency of solar thermochemical H2 production

Solar thermochemical (STC) technology utilizes the entire spectrum of solar energy to decompose water to produce hydrogen. This technology reduces carbonic fuels, nearly only producing hydrogen rather than hydrogen-oxygen mixture. However, low water-splitting activity of redox materials restricts improvement of water-hydrogen conversion ratio and fuel production efficiency. Recently, a kind of perovskite LaFeO₃ attracts attention, because of the good performance in photocatalysis hydrogen production. Nevertheless, how LaFeO₃ system works in STC water-splitting cycle is rarely studied. In this paper, the first principle method at density functional theory level is adopted to reveal the hydrogen production mechanism of perovskite LaFeO₃ doped with 25% Sr/Ca at A site. Hydrogen migration on material surface determines hydrogen generation rate. The activation energy of 25%-Ca-doped LaFeO₃ is relatively lower 150.09 kJ/mol. In addition, fuel production efficiency has been calculated. When water to hydrogen conversion ratio is 100%, solar-to-fuel efficiency can reach maximum 0.472. The effect of water-splitting kinetics on hydrogen production is also discussed. The results indicate that when T_red = T_oxi = T = 1200K and water to hydrogen conversion ratio is 10%, the dynamic efficiency of La_0.75Ca_0.25FeO₃ can reach 20%. This research can provide index for improving the hydrogen production performance of STC technology.     

Development of European hydrogen infrastructure scenarios—CO2 reduction potential and infrastructure investment

For the introduction of a hydrogen economy one of the most relevant questions is: what are the suitable feedstocks and production technologies for hydrogen, which is a secondary energy carrier, taking into account the manifold objectives of hydrogen introduction: the cost-effective substitution of oil, increasing the security of energy supply, and reducing CO₂ and other emissions? This study focuses on constructing a hydrogen infrastructure in Europe by 2030. Several hydrogen technologies and their integration into an infrastructure system, including the production, transport and distribution of hydrogen, are analysed on the basis of energy chain calculations and expert judgements and consistent scenarios are developed. It can be shown that under economic and CO₂-reduction objectives, the steam reforming of gas, followed by coal gasification and, to a limited extent, the electrolysis of electricity from renewable energy carriers are the most promising hydrogen production options in this first phase for developing a hydrogen infrastructure. These options result in a significant level of CO₂-reduction. However, the total cost of the infrastructure will account for 0.3% of EU-25 GDP in 2030. This shows the extent of the challenge involved in constructing a hydrogen infrastructure.     

Hydrogen gas production from waste anaerobic sludge by electrohydrolysis: Effects of applied DC voltage

Waste anaerobic sludge was subjected to different DC voltages (0.5-5 V) for hydrogen gas production by using aluminum electrodes and a DC power supply. Effects of applied DC voltage on the rate and extent of hydrogen gas production were investigated. The highest cumulative hydrogen production (2775 ml), daily hydrogen gas formation (686.7 ml d⁻¹), hydrogen yield (96 ml H₂ g⁻¹ COD) and percent hydrogen (94.3%) in the gas phase were obtained with 2 V DC voltage. Energy conversion efficiency (H₂ energy/electrical energy) also reached the highest level (74%) with 2 V DC voltage application. Control experiments with no voltage application to the sludge yielded almost the same level of COD removal, but no hydrogen gas production. Voltage application to water resulted in much lower hydrogen gas production as compared to sludge indicating negligible electrolysis of water. The results indicated that the sludge was naturally decomposed by the active cells removing COD and releasing hydrogen ions to the medium which reacted with the electrons provided by DC current to produce hydrogen gas. Hydrogen gas production from electrohydrolysis of waste sludge was found to be a fast and effective method with high energy efficiency.     

Photocatalytic degradation and hydrogen evolution using bismuth tungstate based nanocomposites under visible light irradiation

In this work, Bi₂WO₆/PANI composites were synthesized for efficient removal of ciprofloxacin (CIP) from urban wastewater and production of hydrogen energy in the absence of sacrificial agents. The experimental study visualizes the formation of 2D based nanostructures and perceived that these nanostructures could provide more photocatalytic active-sites for removal of CIP and also increase the oxidation/reduction of water for hydrogen energy production. The PXRD showed excellent crystallinity/orthorhombic structure with crystallite size 10–23 nm. The Bi₂WO₆/PANI composites, compared to Bi₂WO₆, exhibited higher efficiency and stability for degradation of CIP and production of hydrogen energy. CIP was effectively degraded 98% by Bi₂WO₆/PANI (5%) and the effect of different parameters such as pH, catalyst-concentration, and effect of CIP-concentration was also analyzed. The hydrogen energy rate was 490.56 h⁻¹g⁻¹ by using Bi₂WO₆/PANI (5%). The improved photocatalytic performance of Bi₂WO₆/PANI composite was mainly ascribed to the unique hierarchical structures, harvesting extended absorption of visible light, higher surface area, and higher crystallinity. The current findings may provide new insights to fabricate nanomaterials for environmental and energy issues.     

A brief look at three decades of research on cyanobacterial hydrogen evolution

Hydrogen evolution by cyanobacteria is a potential way of biohydrogen production for the future. The basic and early applied research over the last 30 years has established the basis of present knowledge in the field and is a platform for future R&D directions. This work briefly surveys some of the progress made in the field of cyanobacterial hydrogen evolution during this time period.     

Effect of g-C3N4 amount on green synthesized GdFeO3/g-C3N4 nanocomposites as promising compounds for solid-state hydrogen storage

Hydrogen energy is a key role in novel renewable energy production/consumption technologies. Traditional hydrogen energy systems are suffered from low density, high production cost, low efficiency, and storage complications. With the start of solid-state hydrogen storage technology, many of above deficiencies are fulfilled, however, there are several unknown points, particularly in metal oxides, which need more attention. Hydrogen sorption on the layered materials or inside porous materials is a hopeful key to drawbacks for high-performance hydrogen sorption. Hereupon, layered solids with the merit of hydrogen sorption are introduced, for the first time, including “nanostructured bi-metal oxide (BMO)” and “graphitic carbon nitride (CN)”. Perovskites are ceramic and they are hard materials so they could be a favorable candidate for solid-state hydrogen storage. g-C₃N₄ has attractive features including high surface area, chemical stability, small band gap, and low-cost synthesis methods but also has great potential as an electrode material for energy storage capacitors. The main motivation for this study comes from the potential applications for perovskite materials and graphitic carbon nitride for the solid-state hydrogen storage method. The Perovskite type GdFeO₃ nanostructures (as BMO) synthesized through sol-gel approach in front of natural source of Grape juice as both complexing agent and fuel. The experimental scrutinization ascertains an original fabrication of GdFeO₃ (GF) nanostructures in Grape juice at 800 °C, with an approximately uniform nanosized structure of 70 nm on average. The obtained pure GF nanostructures are then utilized for nanocomposite formation based on g-C₃N₄ (CN) with different amounts. The resulting nanocomposites with the ratio of 1:2 from GF:CN perform a preferable hydrogen sorption capacity, in terms of “maximum discharge capacity of 577 mAhg^?1” in 2 M KOH electrolyte. It should be declared that however, the discharge capacity of the nanostructured GF is 188 mAhg^?1. It can be emphasized that these GF/CN nanocomposites can be utilized as hopeful hosts in an electrochemical hydrogen storage setup due to the synergic effect of g-C₃N₄ with essential characteristics in cooperation with BMO nanostructures as acceptable electrocatalysts.